1. Field of the Invention
The invention relates to brine seals for filter assemblies and, more particularly, relates to brine seals for tubular filter assemblies connectable to a filter manifold and to filter assemblies incorporating such brine seals.
2. Discussion of the Related Art
Tubular filter assemblies are widely used in drinking water filtration systems and the like. Two or more such assemblies are typically connected to a single manifold with each filter providing a different type of treatment. At least one filter of such systems typically comprises a so-called reverse-osmosis filter assembly having a tubular, typically rolled filter element connected to a manifold having an untreated water inlet port, a treated water outlet or discharge port, and a brine or rinse water outlet or discharge port.
One such water filter assembly is disclosed in U.S. Pat. No. 5,002,664 which issued on Mar. 26, 1991 in the name of Robert A. Clack et al. ("the Clack patent"), the subject matter of which is hereby incorporated by reference. Referring now to FIG. 1, a water filtration system 10 of the type disclosed in the Clack patent includes a manifold 12 and a reverse-osmosis filter assembly 14. Filter assembly 14 includes a tubular filter element 16 formed from a rolled filter membrane and encased in a sump or housing 18 connected to a boss 20 of the manifold 12 by a sump nut 22. Untreated water is fed from the manifold 12 into an inlet 24 formed in the bottom of housing 18 via an external feed line 26. Water is treated in filter assembly 14 in a manner which is, per se, well known, with treated water returning to the manifold 12 via a male fitting 28 extending from filter element 16 and cooperating with a corresponding female fitting 30 depending from manifold 12. Rinse water returns to the manifold 12 by flowing through a passage 32 formed between the boss 20 and the fittings 28 and 30.
A brine seal 34 is provided proximate the lower end 36 of tubular filter element 16 so as to assure that water flows into the lower axial end 38 of filter element 16 rather than directly into the rinse water passage 32. Brine seal 34 includes a body 40 and a skirt 42 which sealingly engages the inner peripheral surface of housing 18.
The filter assembly 14 of FIG. 1 incorporating the brine seal 34, while providing adequate water treatment, exhibits several disadvantages. For instance, feed line 26 is not only aesthetically unattractive, but may also be subject to puncture and breakage, and also requires the use of relatively complex fittings connecting the feed line 26 to bottom inlet 24 of housing 18. This inlet 24 and the associate fittings 44 may be subject to leakage problems when the housing 18 is pressurized during operation of the water filtration system. Moreover, it has been found that, due to the relationship between the water feed passageway including an internal shutoff valve and the external feed line 26, harmonics may arise in the system upon start-up which create bothersome vibrations and noises.
In addition, the location of the brine seal 34 on the lower end 36 of filter element 16 may hamper assembly of the filter assembly 14. That is, unless care is taken when inserting the housing 18 over the brine seal 34 on the filter element 16, the skirt 42 of brine seal 34 may bend upwardly, thus destroying the effectiveness of the seal and rendering the filter assembly 14 inoperable for its intended purpose.
Providing a brine seal 34 on the lower end of the filter element 16 also decreases the capacity of filter assembly 14 if an injection molded housing 18 is employed. Injection molded elements are necessarily tapered from their upper to their lower ends. It is therefore necessary to decrease the diameter and thus the capacity of the filter element 16 to assure adequate clarence between the filter element and the housing in the vicinity of the brine seal 34.
Moreover, water pressure between the skirt and the filter element tends to force the brine seal away from the element, thus threatening the integrity of the seal, particularly if the seal is secured to the filter element by taping.
Still another disadvantage resides in the fact that brine seal 34 is also incapable of reenforcing the upper axial end of the filter element 16, thus requiring the employment of an additional reenforcement device to prevent the rolled filter membrane from telescoping during use.
Other known filtration systems eliminate the feed line by employing a specially designed filter element in which the untreated water inlet, rinse water outlet, and treated water outlet are all formed in the upper axial end of the filter element with the waste or rinse water and treated water being discharged from concentric tubes. This arrangement is complex and thus relatively expensive to fabricate.